The number of global and national coronavirus cases isn’t the only thing changing on a daily basis; so is our understanding of the behavior of the coronavirus and its transmission.
For months, the World Health Organization (WHO) has stated that COVID-19 spreads mainly through direct contact with large respiratory droplets, especially those created when a sick person coughs or sneezes. The WHO’s advice largely informed current safety guidelines, such as wearing a mask in public places and remaining six feet apart from others.
However, 239 scientists from more than 30 countries recently signed a letter published in Clinical Infectious Diseases asking the WHO to consider the serious potential of airborne COVID-19 transmission.
Is There Evidence of Airborne Transmission?
Though the WHO has focused on the spread of COVID-19 through large respiratory droplets, a large swath of the scientific community believe that people can become infected with the coronavirus after inhaling tiny respiratory droplets lingering in the air.
Authors of ”It Is Time to Address Airborne Transmission of COVID-19,” Lidia Morawska and Donald Milton, wrote, “There is significant potential for inhalation exposure to viruses in microscopic respiratory droplets (microdroplets) at short to medium distances (up to several meters, or room scale), and we are advocating for the use of preventive measures to mitigate this route of airborne transmission.”
“We wanted [the WHO] to acknowledge the evidence,” Jose Jimenez, a chemist at the University of Colorado who signed the paper, explained. “This is definitely not an attack on the WHO. It’s a scientific debate, but we felt we needed to go public because they were refusing to hear the evidence after many conversations with them,” he said.
According to Morawska and Milton, studies have demonstrated “beyond any reasonable doubt” that viruses are released when people exhale, talk, and cough. Those microdroplets are so small that they can remain in the air and pose a risk of exposure to others, even from a “safe” social distance.
WHO Confirms the Possibility of Airborne Transmission
The WHO responded to Morawksa, Milton, and their scientific community shortly after their open letter was published.
“We have been talking about the possibility of airborne transmission and aerosol transmission as one of the modes of transmission of COVID-19,” Maria Van Kerkhove, technical lead on the COVID-19 pandemic at the WHO, explained in a news briefing.
However, the WHO is not ready to definitively confirm the role of airborne transmission in the coronavirus pandemic. Benedetta Allegranzi, the WHO’s technical lead for infection prevention and control, elaborated on this during a news briefing in Geneva on July 7.
“The possibility of airborne transmission in public settings- especially in very specific conditions, crowded, closed, poorly ventilated settings that have been described, cannot be ruled out. However, the evidence needs to be gathered and interpreted, and we continue to support this.”
What Needs to Change to Prevent Airborne Transmission?
If Morawska, Milton, and other scientists are correct, the precautions we currently use to safeguard against COVID-19 may not be enough.
Current guidelines focus on hand washing, social distancing, and face masks. While these are all important precautions, Morawksa and Milton wrote, they are “insufficient to provide protection from virus-carrying respiratory microdroplets released into the air by infected people.”
They recommend the following additional measures to maximize safety and limit the growing number of coronavirus cases in the U.S:
- Provide sufficient and effective ventilation in public buildings, workplace environments, schools, hospitals, and nursing homes
- Supplement general ventilation with airborne infection controls such as local exhaust, high efficiency air filtration, and germicidal UV lights
- Avoid overcrowding in public transportation and buildings
As the authors emphasize, working with the WHO to establish the true methods of COVID-19 transmission is of “heightened significance” now, when countries are reopening following lockdowns and bringing citizens back into schools and workplaces.